There are two keys to painting ceramic tile.

The first is the cleaning of the tile. The tile and the grout must be absolutely clean before you paint. If there is dirt on the tile or grout or any type of film on the tile, the paint will not adhere well and it will peel. Get a good cleaner and scrub well to remove all of the dirt. When you are done cleaning, wait at least 2 days before painting so that the grout has time to completely dry.

The second key to painting tile is to use the right type of paint. The best paint to use is an oil-based paint. It will stick the best to tile and last for many years. If you can't find oil-based paint or you don't want to deal with the clean-up that this requires, the second best choice is to use a water based paint that includes a urethane resin. While not quite as good as the oil-based paint, this is a good second choice and it will be much easier to clean up afterwards.